1. Field of the Invention
The present invention relates to a method of accessing a medium with low power consumption by means of standby function and a recording/reproducing apparatus for realizing this method.
2. Description of the Related Art
Conventional recording/reproducing apparatuses such as floppy disk drives have a standby function, as is disclosed in U.S. Pat. Nos. 4,700,234 and 4,688,112, both issued in 1987. In these apparatuses, after the power switch has been turned on, no power is supplied to the read/write circuit until the rotational speed of the spindle motor for rotating magnetic recording medium rotates reaches a predetermined value after the spindle motor starts rotation in response to a read or write command. In addition, no power is supplied to the read/write circuit whenever the magnetic heads seeks a destination track on the recording medium in response to the seek command. As a result, power consumption is reduced.
Typical recording/reproducing apparatuses have two magnetic heads, S0 and S1, disposed one above the other and facing each other, both being supported by a carriage. At the time the heads is subject to a seek operation, the carriage is moved in the radial direction of a magnetic recording medium; actually, the magnetic heads are moved by a head driving mechanism (carriage driving mechanism) using a stepping motor, by the distance corresponding to the number of step pulses supplied from a floppy disk controller (FDC) to the stepping motor (i.e., by the number of tracks). Normally, the magnetic heads are moved by one track with respect to a 1 step pulse, for example. When the 1 step pulse is output to the stepping motor from the FDC to move the magnetic heads to an adjacent track, therefore, the standby state will always be set and the power supply to the read/write circuit will be stopped.
However, in this standby system, after an adjacent track is sought as a destination track, the magnetic head accesses to this track for a read/write operation, access to a sector immediately upon completion of the seek operation may not be possible. As a result, the apparatus cannot access the medium until that sector makes one revolution. According to a format of tracks on the magnetic recording medium, gap areas GAP exist between sectors, with GAP 3, GAP 4, and GAP 0 normally existing between the head or first sector and the last or 36th sector. Each gap area corresponds to a rotational time of approximately 11 ms for a 1-MB magnetic recording medium, approximately 6.3 ms for a 2-MB type, and approximately 5.4 ms for a 4-MB type. The standby time (time for stopping the current supply from the power supplier) is set to, for example, around 8 ms (which is longer than the interval between step pulses) after a step pulse is output. Therefore, in a case of a low-recording density recording medium, such as a 1-MB type, data can be read from the first sector of an adjacent track subsequent to the last sector of a current track after the adjacent track is sought. However, when a relatively high-recording density recording medium, such as a 2-MB or 4-MB type is used, a wait state for one rotation occurs after an adjacent track is sought. Specifically, in the case where a file extending over two adjacent tracks is recorded on a magnetic recording medium, data is read out from the last sector of the first track by the magnetic head S1, then data is read out from the first sector of the second track by the magnetic head S0. In such a case, the FDC outputs one step pulse to the stepping motor to permit the associated magnetic head to seek the adjacent, second track after data is read out from the 36th sector of the first track. Then, the next data is read out from the first sector of the second track.
According to the conventional standby system, in executing a consecutive read/write operation over adjacent two tracks, a time loss corresponding to one rotation of the magnetic recording medium is generated when the read/write operation is carried out after seeking the adjacent tracks by the associated magnetic head.